Block copolymers comprising polyoxymethylene units, in addition to other polymer and polycondensate units, are described for example in GB 807589, EP 1 418 190 A1, U.S. Pat. No. 3,754,053, US 2002/0016395, JP 04-306215, GB 1164997 and U.S. Pat. No. 4,352,914. The other polymer or polycondensate units present, in addition to polyoxymethylene units, comprise polyalkylene glycol units, in particular polytetramethylene glycol and polyethylene glycol units, also vinyl acetate-crotonic acid copolymers, methyl methacrylate-vinyloxyethylamine copolymers, vinyl acetate-allyl acetoacetate copolymers, vinyloxyethylamine-isobutyl methacrylate copolymers, dihydroxylated polybutadiene and difunctionalized polyethylene units.
Polyethercarbonates having at least one Zerewitinoff-active hydrogen atom can be prepared by catalytic reaction of alkylene oxides (epoxides) and carbon dioxide in the presence of H-functionalized starter substances (“starters”) and has been the subject of intensive study for more than 40 years (e.g. Inoue et al., Copolymerization of Carbon Dioxide and Epoxide with Organometallic Compounds; Die Makromolekulare Chemie 130, 210-220, 1969). This reaction is shown in schematic form in scheme (I), where R is an organic radical such as alkyl, alkylaryl, arylalkyl or aryl, each of which may also contain heteroatoms, for example O, S, Si, etc., and where a, b, c and d are each integers and R may differ in different repeating units, and where the product shown here in scheme (I) for the polyethercarbonate should merely be understood in such a way that blocks having the structure shown may in principle be present in the polyethercarbonate obtained, but the sequence, number and length of the blocks and the OH functionality of the starter may vary, and is not restricted to the polyethercarbonate shown in scheme (I). This reaction (see scheme (I)) is environmentally very advantageous, since it constitutes the conversion of a greenhouse gas such as CO2 to a polymer. A further product, actually a by-product, formed here is the cyclic carbonate shown in scheme (I) (for example, when R═CH3, propylene carbonate).
